Life Cycle Study of Production of Renewable Diesel : A LCA Comparison Between Hdrodeoxygenation and Catalytic Decarboxylation Processes

Two of the main processes for production of long chain liquid hydrocarbons from fatty acids are hydrodeoxygenation (HDO) and catalytic decarboxylation (decox). The aim of both these processes is to remove oxygen form the carboxylic group of the fatty acid to produce saturated liquid hydrocarbons. The reaction for both processes is done in a semi-batch reactor using an alkaline catalyst. The main difference between these two processes is that in the HDO, a constant stream of pure Hydrogen gas is used to hydrogenate and retard deactivation of catalyst. However, in the deCox, a mixture of hydrogen and inert gas (e.g. Nitrogen or Argon) is used, with the weight percent of hydrogen varying from 5 to 10. As production of hydrogen is an energy-intensive process, it is deemed that the emissions of producing biofuel using the deCox approach would reduce greenhouse gas emissions compared with conventional HDO. In this work the environmental impact of both these processes are assessed and the results are compared accordingly. It is shown that the greenhouse gas emissions of deCox process is lower compared to conventional HDO.